Solar Orbiter Heliospheric Imager (SoloHI)

Direct Access to Data

Data recorded by the SoloHI instrument during the remote sensing windows of the science phase of the Solar Orbiter mission have been publicly released. The data are generally made public at most three months from the date that all telemetry from that period has been received on the ground. 

SoloHI Data User Guide

SoloHI IDL routines are available in SSW at $SSW/so/solohi/idl 

These routines allow for reading SoloHI FITS files, combining tiles into the full mosaic, and processing movie cubes. 

Basic Examples in SSWIDL:

Read a SoloHi fits file and get a header structure/image array:

shireadfits, file, hdr, img

Read a SoloHI summary file to find specific files. Returns a data structure with the information from the summary file. Will require the summary file to be in the expected location relative to the data or supplied by the user. A level can be 'L1' or 'L2'.

data=solohi_read_summary(yyyymdd, level=level, sumpath=sumpath)

Read multiple SoloHI summary files to get data over range of dates, can also be used to narrow selection to specific file types and can get the path to the file and add it into data.filename

data=solohi_summary_range(yyyymmdd_start, yyyymmdd_end, /get_path, level=level)

Combine individual tiles into a single SoloHI mosaic (files must be a list of 4 fits files, 1 from each tile, to work properly)

mosaic=solohi_fits2grid(files)

Create a movie of mosaics from a list of files. Can create running ratio or running difference movies with ratio or rdiff keywords.

solohi_mosaic_movie, files, /ratio

Available Data

Data is currently available through March 12, 2023.

Data Formats/Products

We are making several data products available including raw and processed images (science data and PNGs), and movies (animations) in different formats. The science data is provided in the FITS (Flexible Image Transport System), for which three different products are available: Level-1, Level-2, and Level-3, described below.

  • Level-1 (L1): de-compressed, uncalibrated image data with no correction applied, except for rectification, so that solar north is (approximately) up. Data units are DN.
  • Level-2 (L2): calibrated data in units of Mean Solar Brightness (MSB), with bias, stray light, and vignetting corrections applied.
  • Level-3 (L3): L2 images with the F-corona removed to highlight solar transients. These files are currently under development. 
  • Summary Files: Daily files containing a list of observations and some basic information about each image.

File Name Format

SoloHI filename: solo_L#_descriptor-YYYYMMDDHHMMSS_V#.fits
where:

  • L# = processing level
  • V# = version number of the file
  • descriptor = data descriptor of format 'solohi-XYZ', where each "XYZ" character encoding provides different information about the file, as shown in the Table below.
SoloHI Data Descriptor Definitions
X Y Z
Value Definition Value Definition Value Definition
1 Tile 1 f Full-field without bias subtraction b Bias Image
2 Tile 2 g Full-field with bias subtraction h Header Only
3 Tile 3 u Subfield without bias subtraction s Sum of multiple exposures, full-resolution
4 Tile 4 v Subfield with bias subtraction t Sum of multiple exposures, binned
m Mosaic of all tiles     f Single exposure, full resolution
        g Single exposure, binned

Choosing your data product

In most circumstances, we recommend the use of the Level-2 or Level-3 data products for essentially all scientific analyses, both qualitative and quantitative. The PNG and mpg movie formats are appropriate for browsing the data but should not be used as quantitative science tools.

Data Access

SoloHI movies files: https://solohi.nrl.navy.mil/so_data/movie/

Direct access to L1 FITS files: https://solohi.nrl.navy.mil/so_data/L1/

Direct access to L2 FITS files: https://solohi.nrl.navy.mil/so_data/L2/

Direct access to Daily Summary files: https://solohi.nrl.navy.mil/so_data/summary/

SoloHI Background-Removed Movies: https://solohi.nrl.navy.mil/so_data/movie/jpl

Background removal on SoloHI images is complicated by the fact that the background (stray light, F-corona) changes whenever the orientation of either the spacecraft or the solar arrays changes. In addition, reflected light from the solar arrays makes some regions at the inner edge of the two inner tiles (Tiles 1 and 2) unusable, so these pixels must be masked. The approach and movies found here use a statistical approach to remove the backgrounds and create the masks.

Documented software to remove the backgrounds and create background-removed images, movies, and FITS files is available via SolarSoft in the SoloHI tree. A presentation describing the process, software, and resulting products can be found here (6.1MB PDF).

The link to SoloHI full field-of-view background-removed movies in helioprojective cartesian coordinates is https://solohi.nrl.navy.mil/so_data/movie/jpl

Data release history notes

October 16, 2023: All Files released before September 30, 2023 (this includes all files from the beginning of the mission through March 12, 2023) were released with incorrect observation times. The files have all been re-released with corrected times. Because the file names are derived from the observation time, the file names have all been changed. If you believe you may have downloaded data at the incorrect times, compare the files you have with what we currently have provided for the same time period. If the file names are the same (though possibly with a different version number), then you should have the corrected files. Otherwise, you will need to download the data again. 

Acknowledgments

Solar Orbiter is a mission of international cooperation between the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA), operated by ESA. 

The Solar Orbiter Heliospheric Imager (SoloHI) instrument was designed, built, and is now operated by the US Naval Research Laboratory with the support of the NASA Heliophysics Division, Solar Orbiter Collaboration Office under DPR NNG09EK11I. The NRL effort was also supported by the Office of Naval Research.

Solar Orbiter has an open data policy. 

The appropriate journal reference to use for SoloHI data is Howard, R. et al. (2020), The Solar Orbiter Heliospheric Imager (SoloHI), A&A, 642, 23, https://doi.org/10.1051/0004-6361/201935202

 

WISPR Pub Number 1